Don't do it. Steel would be OK, depending on how bad, but with Aluminum you're just asking for it.
Speaking of asking for it, I should really get a new fork.
henry
Posted: Tue Apr 11, 2006 2:45 pm
somewhat piggishJoined: 05 Aug 2005Posts: 5415Location: on porch with shotgun
dennyt wrote:
Don't do it. Steel would be OK, depending on how bad, but with Aluminum you're just asking for it.
Speaking of asking for it, I should really get a new fork.
yeah that's what i figured. Although i'm sure aaron will be like "mmmm just bend it until it feels like it's at home again and take off your helmet, then you'll be fine"
How do you think they make them in the first place. Alumunum has a very low fatigue life. Most handlebars are not heat treated.
lantius
Posted: Wed Apr 12, 2006 4:43 pm
1337Joined: 22 Jul 2005Posts: 6705Location: right over
Aaron wrote:
Aluminum Bars can be bent back ONCE.
How do you think they make them in the first place. Alumunum has a very low fatigue life. Most handlebars are not heat treated.
yeah, i'm going to hold out to hear what people who don't have ridiculous ideas about metallurgy have to say.
zuvembi
Posted: Wed Apr 12, 2006 4:51 pm
Joined: 24 Jul 2005Posts: 942Location: Little Addis Ababa
lantius wrote:
Aaron wrote:
Aluminum Bars can be bent back ONCE.
How do you think they make them in the first place. Alumunum has a very low fatigue life. Most handlebars are not heat treated.
yeah, i'm going to hold out to hear what people who don't have ridiculous ideas about metallurgy have to say.
Disclaimer: I'm no metallurgist, but...
The standard answer is that bending it back is just weakening them twice as much for aluminum handlebars. i.e. unless you like dental work and are trying to hook-up with your oral reconstructive surgeon, maybe handlebars aren't the best place to cheap out on safety.
_________________ When the revolution comes, we're going to need a longer wall
SeditiousCanary
Posted: Wed Apr 12, 2006 4:56 pm
sorry, can't make it!Joined: 26 Jan 2006Posts: 2315Location: Fremont Troll
zuvembi wrote:
i.e. unless you like dental work and are trying to hook-up with your oral reconstructive surgeon, maybe handlebars aren't the best place to cheap out on safety.
Hi! My name is Henry. I like butterflies, oral reconstruction, and tuba players...
somewhat piggishJoined: 05 Aug 2005Posts: 5415Location: on porch with shotgun
SeditiousCanary wrote:
zuvembi wrote:
i.e. unless you like dental work and are trying to hook-up with your oral reconstructive surgeon, maybe handlebars aren't the best place to cheap out on safety.
Hi! My name is Henry. I like butterflies, oral reconstruction, and tuba players...
I stand by what I said. Handlebars that break are ones ridden for THOUSANDS of miles or really cheap shitty ones (Daniel's bars may have been cheap, I don't know. He did ride for thousands of miles. Also a loose bar clamp bolt would weaken the bars). If there is a kink in the bar then no way, but a mild bend is fine to pull out. Most people do not have the feel or skill to do it. I have been bending metal for 20+ years. Forks, frames, spokes, rims etc. It is perfectly OK to bend an aluminum rim out and they have been heat treated! A bicycle is a very forgiving machine and most of the parts are way overbuilt for the stresses involved (otherwise they would fail right a way). You would not believe the state of some of the bicycles I have seen ridden into my shop. I would like to see Henry's bars before I attempted to bend them. That said, ALL bicycle parts should be inspected before each and every ride. Read any owner's manual or product information. The people that get into trouble are the ones that do not LISTEN to their bike (or body for that matter).
Hayduke
Posted: Wed Apr 12, 2006 6:21 pm
Joined: 01 Feb 2006Posts: 677Location: Seattle, WA
I have actual training as an acft mech and when it comes to doubt we through the shit out. That said, there is nothing wrong with a little NDT. I am sure once we get this "shop" up and running we can set up a dye penetrant and mag test to check for those nasty as micro fractures. Also, as a climber I have seen the odd ATC or locking beener just fucking snap. So, as much as I appreciate aluminum for its lightness I trust it about as much as I trust my ex-wife. NUFFF SAID!!!!
zuvembi
Posted: Thu Apr 13, 2006 10:38 am
Joined: 24 Jul 2005Posts: 942Location: Little Addis Ababa
Aaron wrote:
I stand by what I said. Handlebars that break are ones ridden for THOUSANDS of miles or really cheap shitty ones
I've broken both in the past year, one was some cheap shitty OEM ones on a old French bike, the other had probably had about 9-10,000 miles on them.
Quote:
Forks, frames, spokes, rims etc. It is perfectly OK to bend an aluminum rim out and they have been heat treated! A bicycle is a very forgiving machine and most of the parts are way overbuilt for the stresses involved (otherwise they would fail right a way).
These are hugely different examples, and are we talking about steel or aluminum? Because I'm strictly talking aluminum. If you're talking steel, I agree you absolutely can cold-set steel perfectly safely. Half my frames/bikes have had the rear spacing changed.
As to the parts being overbuilt, I have a different opinion, but I seem to be a statistical outlier.
Rims are a different case altogether as the forces on them are a lot different than a stem/handlebar/fork. Also if your rim cracks or breaks it's rarely something that makes you do a faceplant like a stem or handlebar failure can. Aren't rims quite a different alloy mix than what's used for stems/handlebars/frames?
_________________ When the revolution comes, we're going to need a longer wall
Aaron
Posted: Thu Apr 13, 2006 1:29 pm
Joined: 25 Jul 2005Posts: 4645
Sometimes you just have to get on with your life. Bending parts with a little skill is no big deal. I am not going to say anymore until I actually see Henry's bars. The same thing was said about Sean's Cannondale. Need to see first before any judgement can be made. Mechanic's all over the world have been straightening aluminum parts for decades with success. Engineering is one thing, the real world is another. Galloping Girdy!
gregas
Posted: Thu Apr 13, 2006 1:34 pm
Joined: 04 Aug 2005Posts: 260Location: seattle
Henry, Get these bars. I think they are more tame.
1337Joined: 22 Jul 2005Posts: 6705Location: right over
Aaron wrote:
Galloping Girdy!
isn't galloping gertie an example of people 'just building it' without doing adequate engineering homework? "this bridge design worked the last ten times i've tried it, what could go wrong here?"
dennyt
Posted: Thu Apr 13, 2006 2:29 pm
rocket mechanicJoined: 02 Aug 2005Posts: 2708
This book discusses the design history of suspension bridges, and how the engineering community got to the point that they thought they could get away with the tacoma narrows design (insufficient deck stiffness, and bad aerodynamic design).
And Aaron, even Galileo was wrong about beam bending theory. Check it out!
gr8noise
Posted: Thu Apr 13, 2006 2:46 pm
Joined: 29 Jul 2005Posts: 193Location: Ballard
dennyt wrote:
This book discusses the design history of suspension bridges, and how the engineering community got to the point that they thought they could get away with the tacoma narrows design (insufficient deck stiffness, and bad aerodynamic design).
And Aaron, even Galileo was wrong about beam bending theory. Check it out!
My dad said that when he was in engineering school in the UK they used that as an example of how not to build a bridge.
_________________ Tony D.
There are some things you simply must do.
Aaron
Posted: Thu Apr 13, 2006 3:54 pm
Joined: 25 Jul 2005Posts: 4645
dennyt wrote:
And Aaron, even Galileo was wrong about beam bending theory. Check it out!
I am not saying I would bend just any bar, but straightening handlebars in a real shop practial way is sometimes OK. It depends where the bend is. Near the stem, not a good idea, out near the end is fine. Usually bars bend at the hooks or the first bend out from the stem. Pulling it out may "in theory/textbook" weaken the metal but the bar will be fine.
eternalignorance
Posted: Fri Apr 14, 2006 10:54 am
Joined: 08 Jan 2006Posts: 359Location: Imaginary Places
you guys are nuts.
Aaron
Posted: Fri Apr 14, 2006 1:25 pm
Joined: 25 Jul 2005Posts: 4645
aluminum nuts?
So I was thinking about all the alumunum parts on a bike that I or other mechanics I know (Val for example) have straightened:
Here are some Aluminum parts that should never be straightened
Seatposts
Stems
Forks
Crankarms
All these parts are weakened a little in the process. But since bicycle parts are way overbuilt, some weakening can be tolerated. Bicyle parts are tested on huge fatigue machines that overload the part with at least twice the weight the part is designed. That is why an experienced "feel" for metal is required.
So to be clear, I would not just bend a part back, I would straighten or align it. Last night at Mobius, I felt Henry's bar. It was not moving and to attempt to straighten it would require removing the bars for inspection and clamping in a vise.
I am a very careful and experienced mechanic. I worry about liability and what my mechanics can and can't do. There are some technical people that say if a handlebar even has a scratch that you should not ride it. You have to strike a balance between fixing things and just replacing them as not everyone wants or can afford to buy new every time the part is damaged. If I did align someone's handlebars, I probably would not charge for it. I would also make them aware. Bike part failures always give you a warning if you inspect your parts often and listen to your bike, like you should!
Old Fart
Posted: Fri Apr 14, 2006 1:50 pm
Joined: 23 Feb 2006Posts: 31Location: Cardboard box by the beach
The only way to settle this once and for all is a drunken brawl.
Fuck all that metalurgy shit, last one standing is right!
Edit: The only deeper meaning of this post is that I was bored at work. Drunken brawls can be very entertaining.
Last edited by Old Fart on Sat Apr 15, 2006 11:50 pm; edited 1 time in total _________________ Work Buy Consume Die
henry
Posted: Fri Apr 14, 2006 1:51 pm
somewhat piggishJoined: 05 Aug 2005Posts: 5415Location: on porch with shotgun
Old Fart wrote:
The only way to settle this once and for all is a drunken brawl.
Fuck all that metalurgy shit, last one standing is right!
Gee, I hope I didn't sound like I was trying to be right. Sometimes it is hard to judge the tone people have in their text. Hell, even some people are hard to read in person (Lee). All I am saying is there are shades of grey and many ways to do something. Using skill and judgement of course.
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